Phenylethanolamine N-methyltransferase (EC 2.1.1.128; PNMT) catalyzes the conversion of norepinephrine to epinephrine in the adrenal medulla and, in certain regions of the brain, notably the medulla oblongata and hypothalamus. We have developed a purification procedure for PNMT which allows us to obtain milligram quantities of pure enzyme. Studies on the biophysical characteristics of the enzyme are in progress as is work on characterizing the nature of photoactivated covalent binding of S-adenosyl-L-methionine to the enzyme. We are also studying the effects of pharmacological treatments which raise endogenous S-aenosyl-L-homocysteine levels on PNMT activity, epinephrine levels, and resting blood pressure.